This invention relates generally as indicated to a tire building machine, and more particularly, to certain improvements in tire building machines for positioning the tire beads with precision over both ends of the tire building drum and holding such beads in place during radial expansion of the drum.
In the manufacture of certain types of tires, it is conventional practice to position the tire beads axially and radially over the ends of the tire building drum after the tire plies have been applied to the drum, followed by radial expansion of the drum to expand the tire plies into engagement with the inner diameter of the tire beads as described and shown, for example, in FIGS. 6 and 7 of U.S. Pat. No. 3,721,600, granted to Armindo Cantarutti on Aug. 19, 1970, which is incorporated herein by way of reference.
For precision tire making, it is essential that both tire beads be moved symmetrically about the center line of the tire building drum into the precise positions over the ends of the drum and held in place during expansion of the drum. It is also important in the manufacture of precision tires to obtain the same amount of stitching and turnup of the plies on each side of the tire.
Precise positioning of the tire beads is obtained in accordance with the present invention by providing carriages for the tire beads adjacent both ends of the tire building drum whose movements are controlled by a rack and pinion mechanism including controls and adjustments which cause the carriages to move symmetrically about the center line of the drum to position the tire beads precisely over the ends of the drum where they are held in place during expansion of the drum. The carriages may also include pusher rings and the like to assist in obtaining symmetrical movement of the ply turnup bladders for effecting the same amount of stitching and turnup of the plies on each side of the tire.
It is generally known to use racks and pinions to actuate bead carriers and move the tire beads into engagement with the ends of a tire building drum, but not in conjunction with the controls and adjustments necessary to obtain precise positioning and retention of the tire beads axially over the ends of the drum rather than against the ends of the drum for building a precision tire.